Nowadays, as technologies develop day by day, an audio volume control circuit having AVC is widely applied to various types of electronic products. For example, the audio volume control circuit is applied to a digital television (TV). When intensity of audio broadcasted by the digital TV dramatically changes, e.g., when a channel is changed or an advertisement is inserted, the audio volume control circuit automatically generates an adjustment gain value for adjusting audio volume to maintain the intensity of audio within a predetermined range, so that a user cannot perceive that the audio volume substantially changes when the channel changed or the advertisement is inserted to avoid uncomfortable audio.
Generally, in order to accurately determine an intensity change trend, a conventional audio volume controller needs to calculate an adjustment gain value with reference to a plurality of audio signals. Accordingly, a delay time, td, for controlling the audio signals by the conventional audio volume control circuit may be long. Refer to FIG. 1 showing a signal graph of operations of the conventional audio volume control circuit, and a signal S represents an audio signal controlled by the conventional audio volume control circuit. When an intensity of the signal S is over-increased at a time point T1, the conventional audio volume control circuit only responds to the over-increased intensity at a time point T2 to generate the adjustment gain value to restrain the intensity of the signal S. A period between the time point T1 and the time point T2 is defined as a delay time, td.
In order to solve the problem that the time delay td is too long, the conventional audio volume control circuit needs to define a long buffer to store audio data at these time points. Accordingly, cost of the conventional audio volume control circuit is too high to reduce product competitiveness.